Mark Anderson

Mike thanks so much for helping me with my "other" Porsche. I'm not sure I would have made qualifing without your help.

Mike LaBranche

Mark, it was great fun, happy to help. It seems about half the time I go to a track I end up wrenching on something... and it's always best if you're wrenching for the fast guys. We'll get 'em next time.

S4ordie

Mark K - was LMAO watching you dig around in the shifter cup while still making progress around the lap. I do the same sort of thing but only at the toll both digging for appropriate change. Great video, thanks for sharing them. I am only an arm chair racer and the in-car camera's really make it fun to watch.

Thanks to all of the Rennlister's who campaign Porsches, especailly the 28s.

mark kibort

Thanks! Yeah, a little nerve racking. However, Im getting good practice on getting the transmission back in a gear when "stuff" brakes. Now, I just pull stuff apart and pull the rear shifter rod forward for 3rd! Thats a ball cup, shifter rod and now a shift lever. only a few things left to break.

mark kibort

Here is the RACE 2 video. This is the race where my I blew a brake line and lost all brakes. I drove the last 5 laps with only engine compression. 1:37.5 best lap time for the weekend on Hoosers, and a 1:48 lap time with no brakes, vs 1:45 with only 3rd gear as I had in Race 1. What a weekend!

http://www.youtube.com/watch?v=xYbFeIai2Ng

James Bailey

A single burst brake line should not cause you to not have any brakes it is a dual system for that reason but rear brakes alone would be very weak. I do agree that you should have parked it since you were a potential danger to others.....and yes when you are turning the car wants to slow down...I have my students test that on the skid pad whipping the wheel left then right without the brakes scrubs off a ton of speed. The energy needed to vector the car away from a straight line has to come from the inertia of the vehicle in motion. Getting students to learn that if they are turning but not adding throttle they are slowing down. So what let go on the Cup car ?

Mark Anderson

James Bailey

Ouch , at least it was NOT the engine.

mark kibort

Jim, when the brakes failed, there was no slow down of any substance. we are not talking keeping the car from rolling in the paddock, but slowing a 3000lb mass from 120mph. anyway, there was a slight decel from the pedal, but it turned out to not be worth using as it didnt do anything at the speeds I was traveling at, and the turning braking forces turned out to be much more effective. (as well as compression braking) I did push real hard one time to see what would happen, and near the floor, i could see the rears lock up, but that didnt do anything to really slow me down. One time I pulled the ebrake and it helped a little. watch the video and see what you think. Plus, it is not fullly the vectored direction of the car, but the tirescrub from oversteer. think about it, if you have the tires turned all the way sideways, its like having lock up in front. I was amazed on how well that worked .

James Bailey

Mark full lock on the front end is not " all the way sideways " plus your Devek bar restricts it more and we all know that lightened 928s are nose heavy so the rear brakes never do their fair share. I did watch the video .

mark kibort

i didnt say "full lock". Anyway, my rims hit bar just as the tire hits the chassis, but thats not the point . I was giving an example of where the braking force is coming from. The further you turn the tires, there is a scubbing effect that slows the car quite quickly. I was trying to paint a picture of the car tires sideways, not facing forward. A lot of dynamics , but the net effect is that I can slow the car, as shown in the video, without using brakes pretty effectively. 1:48 lap time with no brakes.

Now, nose heavy has little to do with it, but in fact, it helps to have the weight up front, espeically for this way of slowing a car down. Once you have any deceleration, you have weight transfer to the front wheels. the rears have very little breaking capacity anyway, as we can see with a 1.4g stop. something like only 200lbs per tire in the rear is pressing on the ground. In a turn, trail braking, one tire may even have 0 weight on it. . Hopefully rear brakes never have to do their fair share, that means you are accelerating and using the brakes to generate heat!

Now, a 911 with its weight over the rear wheels and a 40/60 weight distribution, cant avoid a reduced to-the-front weight transfer, but even still,
much more weight is on the front tires in threshold stop.

mk

atb

Mark,
You need one of Colin's ball cup eliminating short shifters.
I'm putting one in the OB.

mark kibort

Just curious, why??

Ive broken the ball cup once and then welded a new one due to the small and very cold weld coming from the factory. Its worked perfect. the plastic insert is not soft when the engine oil is 260f

Ive broken the front shift rod at the torque tube bushing bearing. fluke accident, could have been due to frequent pushing on the gear lever keeping the leather boot on .

Then, I broke the gear shift lever as well, at the two hole openings. (broke in half) It is no surprise, more cold welds from the factory and 1/8" of material holding the structure in tact. re welded by RennSport at the track. better than new.

The only think now to fix is the broken shaft coming out of the rear shifter tube (goes to the tranmission) that also had a cold weld, but the shaft still is trapped in the rear tube mount, so it only makes side to side precise shifting near impossible. I will have that welded soon.


how does the colin ball cup illiminate short shifters? what does that mean. Im confused.

mark kibort

Here are all 3 race videos:

Sorry, didnt get a chance to narrate the "Rear-View-Cam" video, but the other two have comments.

mk

RACE 1 is where the gear shift lever broke after lap 8. Finished the race with just 3rd gear

http://www.youtube.com/watch?v=rKiAu68p8J4

Race 2

http://www.youtube.com/watch?v=xYbFeIai2Ng

and rear view of RACE 2 . This is the RACE where I blow a brake line after lap 8 but still finish the race.

http://www.youtube.com/watch?v=MtFlh0h1G6s

mark kibort

broken shift lever! anyone ever seen this??

all welded up thanks to Rennsport!

mk